Originally Posted by
let-r-eat
OK gentlemen, let's think this out a little so people understand a little about jetting and what is actually happening. When the velocity through the carburetor is LESS you need MORE jet. That's right, an engine that isn't moving any air will need MORE jetting. Let's think about it some more. The air goes through the venturi and creates a depression that pulls the fuel through the booster. Withl less PULL from LESS velocity we will need a LARGER jet. With higher velocity air we will use a SMALLER jet. I want to run a SMALLER jet to achieve stoichiometric within reason.Carburetors are designed to use within a range of jetting. The style of booster used is the biggest contributor. Just think of your carburetor as one of those air blowers that has a hose running into a bucket to draw out parts cleaner or a paint gun that draws from a cup. The velocity of the air/size of venturi/placement of booster in the venturi are what contributes to the jet size. The emulsion metering inside the carburetor adjusts this to the varying velocities/such as WOT verses idle/part throttle.For instance: A very large cam at idle has a bunch of reversion happening that creates a LOW amount of velocity through the venturi with a large carburetor. Downleg boosters create more draw on the circuits than straight leg style booster requiring LESS jet than the straight leg booster would in a similar carb.Hope that helps.
